1,585 research outputs found
Thermoelectric generator fabricated via laser-induced forward transfer
No full textWe show a novel method for the fabrication of a thermoelectric generator with the rapid, lithography-less technique of laser-induced forward transfer (LIFT), performed under ambient conditions. LIFT is a laser-assisted method for the transfer of materials such as metals, semiconductors and dielectrics, where a part of a thin film (donor) previously coated onto a transparent carrier substrate is transferred onto a nearby receiver initiated by the explosive expansion of a small part of the donor volume after the absorption of a laser pulse [1]. Electronic or photonic devices can be fabricated via LIFT on a range of receiver substrates, free from any constraints of substrate properties such as lattice constant or thermal expansion coefficient. This flexibility is desired for applications such as rapid prototyping and the fabrication of devices joining multiple non-standard materials on one substrate. The design of the proposed thermoelectric generator was selected to demonstrate the capabilities of LIFT by transferring layers from the chalcogenide compounds of Bi2Te3 and Bi0.5Sb1.5Te3 onto a glass receiver coated with a polydimethylsiloxane (PDMS) polymer
UV laser direct writing of ferroelectric domain inverted structures in single crystal lithium niobate
No full textFerroelectric domain engineering in lithium niobate (LN) is a subject of extensive research mainly for the fabrication of quasi-phase-matched (QPM) nonlinear optical devices but also for the improvement of linear devices and microstructuring. The most common method for ferroelectric domain engineering is by the application of an external electric field, higher than the coercive field (E Here we present UV laser induced inhibition of ferroelectric domain inversion where spatially selective preexposure of the +z face of congruent LN samples inhibits domain inversion in this area upon the application of an external electric field. In these experiments the two steps of i) UV illumination and ii) E-field application are separated; the application of the external electric field can take place long after (days-months) after the UV illumination
Rapid and mask-less laser-processing technique for the fabrication of microstructures in polydimethylsiloxane
No full textWe report a rapid laser-based method for structuring polydimethylsiloxane (PDMS) on the micron-scale. This mask-less method uses a digital multi-mirror device as a spatial light modulator to produce a given spatial intensity pattern to create arbitrarily shaped structures via either ablation or multi-photon photo-polymerisation in a master substrate, which is subsequently used to cast the complementary patterns in PDMS. This patterned PDMS mould was then used for micro-contact printing of ink and biological molecules
UV laser-assisted fabrication of ridge waveguides in lithium niobate crystals
No full textWe present a UV laser-assisted method for the fabrication of ridge waveguides in lithium niobate. The UV laser irradiation step provides the refractive index change required for the vertical light confinement in the waveguide and also defines the ferroelectric domain pattern which produces the ridge structures after chemical etching
First order quasi-phase matched blue light generation in surface poled Ti-indiffused lithium niobate waveguide
No full textWe report first-order quasi-phase matched blue light generation at 412.66 nm, in a 20mm long surface-poled Ti-indiffused channel waveguide in lithium niobate with cw pumping. 3.46 mW (uncorrected for reflection losses) of blue light has been generated for 70 mW of fundamental power
First-order quasi-phase-matched blue light generation in surface-poled Ti-indiffused lithium niobate waveguides
No full textWe demonstrate efficient first-order quasi-phase-matched second-harmonic generation in a surface periodically poled Ti:indiffused lithium niobate waveguide; 6 mW of continuous-wave blue radiation (=412.6 nm) was produced showing the potential of surface domain inversion for efficient nonlinear waveguide interactions
Ultra-short light-pulse assisted electric field domain engineering of lithium niobate
No full textWhile several techniques to achieve ferroelectric domain inversion in materials such as lithium niobate (LN) and lithium tantalate (LT) have been successfully demonstrated over the past years, even the 'best' established technique of electric field-induced domain inversion (E-field poling) fails when domain inversion at periodicities of a few microns and below are desired. To overcome the limitations associated with electric field poling, we have been investigating the feasibility of an alternative route, which we refer to as light-assisted E-field poling (LAP)
Laser-direct-write technique for rapid prototyping of multiplexed paper-based diagnostic sensors
No full textThe demand for low-cost alternatives to conventional point-of-care diagnostic tools has led to significant developments in the field of paper-based diagnostics, and several methods, which include photolithography, inkjet printing, wax printing etc., have been reported for the fabrication of fluidic devices in porous materials such as paper. Here, we present a simple, laser-based direct-write procedure, which relies on light-induced photo-polymerisation of a photopolymer previously impregnated in the porous substrates for fabrication of the user-defined fluidic patterns within such substrates. During the subsequent development step, the un-polymerised photopolymer is washed-out; however, the hydrophobic polymerized structures that remain in the substrate, and extend throughout its thickness define the barrier-walls of the hydrophilic fluidic patterns they demarcate. These structures contain and guide liquids without any leakage, thus validating the feasibility of using this technique in the production of microfluidic devices. Our results show that for cellulose paper, the minimum widths the hydrophobic barrier-walls should have to successfully contain fluids is ~ 120 µm, and similarly, the minimum dimensions a fluidic channel can have to guide fluids is ~ 80 µm, both of which are the smallest values reported so far. These patterns can be produced rapidly via scanning of a low power continuous-wave laser at speeds of the order of one meter per second and we have successfully implemented it in patterning a range of porous materials including nitrocellulose membranes, glass fibre filter and polyvinylidene fluoride. To further validate the applicability of these laser-patterned devices as sensors, we have demonstrated their use for a range of colorimetric assays including the detection of glucose, protein and nitrite, and also an enzyme-linked immunosorbent assay for detection of C-reactive protein. Finally, we have quantified the speed and cost of our laser-based method and believe that it is suited to up-scaling for mass production
Laser-assisted direct writing of thermoelectric generators
No full textWe present a novel method for the fabrication of a thermoelectric generator using a rapid, lithography-less technique performed under ambient conditions and called laser-induced forward transfer (LIFT). LIFT is a laser-assisted method that has been employed for the transfer of materials such as metals, semiconductors, liquids and dielectrics. A part of a thin film (donor) previously coated onto a transparent carrier substrate is transferred onto a nearby receiver by the explosive expansion of a small part of the donor volume transformed on absorption of a laser pulse. Thereby donor and receiver do not necessarily need to match their lattice or thermal parameters. To demonstrate the capability of LIFT-printing, a thermoelectric generator consisting of staggered p- and n-type doped pads was fabricated by transferring layers of Bi2Te3 and Bi0.5Sb1.5Te3 consecutively onto a glass receiver pre-coated with a thin polydimethylsiloxane polymer film. For a single pair of the generator elements, the thermoelectric voltage per unit degree temperature difference was determined to be >90µV/K. The resistance of a thermoelectric leg pair was in the order of 10kΩ. The performance was compared to that of thermoelectric generators fabricated both with conventional methods and with devices fabricated with different designs using LIFT. The studies show that LIFT is a rapid and novel technique that can be employed for the fabrication of working thermoelectric generators on polymer substrate
Laser-assisted transfer for rapid additive micro-fabrication of electronic devices
No full textLaser-based micro-fabrication techniques can be divided into the two broad categories of subtractive and additive processing. Subtractive embraces the well-established areas of ablation, drilling, cutting and trimming, where the substrate material is post-processed into the desired final form or function. Additive describes a manufacturing process that most recently has captured the news in terms of 3-d printing, where materials and structures are assembled from scratch to form complex 3-d objects. While most additive 3-d printing methods are purely aimed at fabrication of structures, the ability to deposit material on the micron-scale enables the creation of functional, e.g. electronic or photonic, devices [1]. Laser-induced forward transfer (LIFT) is a method for the transfer of functional thin film materials with sub-micron to few millimetre feature sizes [2,3]. It has a unique advantage as the materials can be optimised beforehand in terms of their electrical, mechanical or optical properties. LIFT allows the intact transfer of solid, viscous or matrix-embedded films in an additive fashion. As a direct-write method, no lithography or post-processing is required and does not add complexity to existing laser machining systems, thus LIFT can be applied for the rapid and inexpensive fabrication or repair of electronic devices. While the technique is not limited to a specific range of materials, only a few examples show transfer of inorganic semiconductors. So far, LIFT demonstration of materials such as silicon [4,5] have undergone melting, and hence a phase transition process during the transfer which may not be desirable, compromising or reducing the efficiency of a resulting device. Here, we present our first results on the intact transfer of solid thermoelectric semiconductor materials on a millimetre scale via nanosecond excimer laser-based LIFT. We have studied the transfer and its effect on the phase and physical properties of the printed materials and present a working thermoelectric generator as an example of such a device. Furthermore, results from initial experiments to transfer silicon onto polymeric substrates in an intact state via a Ti:sapphire femtosecond laser are also shown, which illustrate the utility of LIFT for printing micron-scale semiconductor features in the context of flexible electronic applications
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